Blow molding is a well-known fabrication method for thermoplastic components. The process generally involves the molding of a hollow tube, or "parison," of molten thermoplastic that is lowered from an overhanging extrusion head to a position between halves of a reciprocating mold. As the mold halves close, air or some other gas is injected into the parison; the increase in air pressure within the parison caused by such injection forces its walls into the contours of the cavities of the mold halves and thus forms the parison into a desired molded shape. The resulting component has molded walls that surround a hollow chamber. Blow molding has proven to be particularly popular for the production of large parts that would require unduly large molding injection molding machines.
One type of blow molding that has been used successfully for large components that require structural rigidity is the so-called "double-walled" blow molding process. In this process, mold halves are most often designed as distinct core and cavity halves (rather than as two cavities, as would be the case for blow-molded bottles or other containers). The core portion of the core mold half extends within the cavity as the mold halves close. In addition, the mold halves for double-walled components are configured so that the molded components have "full-perimeter flash"; i.e., after molding the component has excess material, or "flash", around the perimeter defined by mating surfaces of the mold halves. This contrasts with single-walled components, in which the parison is inflated entirely within closed mold cavities, and the molded component typically has flash only on its top and bottom portions. Blow-molded components have distinct inner and outer walls that surround a hollow space, with the inner wall having been formed by the core and the outer wall having been formed by the cavity, and with the inner and outer walls being separated by the weld line remaining after the flash is removed. In a typical double-walled component the inner and outer walls are positioned proximate to one another and can have "pinched-off" areas, in which the inner and outer walls are contiguous.
One distinct advantage provided by double-walled blow-molded components is the capability for adjacent regions of the inner and outer walls to differ significantly in their localized contour. For example, a region of the outer wall may have a relatively flat profile, while the adjacent region of the inner wall can contain numerous projections, recesses, and the like, with the profile of either localized region failing to impact significantly the appearance or structural integrity of the other. Such differences in localized inner and outer wall contour are less likely to be successfully achieved in injection-molded components because the inclusion of substantial detail in the inner wall can have a deleterious effect on the dimensional stability, appearance, and even strength of the outer wall. Another performance advantage conveyed by double-walled components stems from the formation of the hollow chamber within the inner and outer walls, as it can provide an air cushion that protects items contacting the inner wall.
For these reasons, double-walled components have proven to be particularly popular for protective containers and carrying cases. Detailed contour that mates with, matches, supports, or captures portions of an item to be carried within the carrying case can be included in the inner wall of the double-walled component even as the outer wall has a generally flat, appearance-sensitive surface. Further, the air cushion between the inner and outer walls helps to protect the item. Thus, the container has the detail and structure necessary to support, transport and protect the item and also provides the desired aesthetic appeal, and does so without the manufacturer having to produce two separate inner wall and outer wall parts.
Many carrying cases have handles to enable the user to more easily pick up, carry, and otherwise manipulate the carrying cases. Some double-walled blow-molded carrying cases include handles that are molded integrally with the body of the case. One example of such a carrying case is illustrated in U.S. Pat. No. 5,361,456 to Newby. The carrying case illustrated therein has a fixed handle that extends away from the body of the carrying case. The handle is formed in each half of the carrying case during the blow molding process by sections of the mold halves that pinch off a portion of the parison that is positioned inward from the outer perimeter of the mold. The pinched-off portion is removed from the molded part to form an opening. The opening and the remaining perimeter portion of the part form the handle for the carrying case.
This design has certain shortcomings, the most prevalent of which is the fact that the handle permanently extends away from the internal storage cavity defined by the halves of the carrying case. In this configuration, the handle cannot be folded to a less extended position for easier storage.